Product and process



PRODUCT AND PROCESS Ralph K. Iler, Wilmington, Del, assignor to E. i. duPont de Nemours and Company, Wilmington, Deh, a corporation of DelawareNo Drawing. Application March 6, 1952, Serial No. 275,233

9 Claims. (Cl. 106-368) This invention relates to surface-modifiedsiliceous solids and to their preparation. The invention is moreparticularly directed to inorganic siliceous particles having an averagespecific surface area of at least 1 square meter per gram, havingchemically bound to the silicon atoms on the surface of said particlesat least 100 OR groups per 100 square millimicrons of surface area ofthe siliceous solid, where R is a substituted hydrocarbon radical havingfrom 2 to 18 carbon atoms and in which the carbon attached to oxygen isalso attached to at least one hydrogen atom, said radical containing abasic substituent attached to a carbon atom at least 1 carbon atomremoved from the oxygen atom of the OR group, the basic substituentbeing selected from the class consisting of nitrogen and sulfur atomscapable of forming onium ions.

According to the present invention siliceous solids having basicreacting surfaces can be prepared by chemically reacting substrateparticles of inorganic siliceous material having an average specificsurface area of at least 1 square meter per gram with a substitutedprimary or secondary alcohol containing amino nitrogen or sulfoniumsulfur and having from 2 to 18 carbon atoms, the nitrogen or sulfursubstituent being attached to a carbon atom at least 1 carbon atomremoved from the hydroxyl group.

The products of the invention are a specific kind of siliceous solidswhich find particular use as adsorbants for acidic materials. Some ofthese solids are often called herein estersils. Estersils are solidsmade by chemically reacting alcohols with certain supercolloidalsiliceous solids. The reaction I have called esterification and thechemically bound OR groups containing a basic reacting substituentresulting from the esterification I have called substituted estergroups.

For a detailed description of estersils prepared from primary andsecondary unsubstituted monohydric alcohols, reference is made to mycopending U. S. application Serial No. 171,759, filed July 1, 1950 nowabandoned, or to Iler U. S. Patent 2,657,149, issued October 27, 1953,as a continuation in part of said application Serial No. 171,759, inwhich estersils of that class are claimed.

THE SUBSTRATE The materials used to form the skeleton or internalstructure, the so-called substrate, of the products of my invention aresolid inorganic siliceous materials. They contain substantially nochemically bound organic groups. They have reactive surfaces which Ibelieve to result from surface silanol (-SiOH) groups. The substratematerials can be mineral or synthetic in origin. They can be amorphoussilica. They can be water-insoluble metal silicates. They can bewater-insoluble metal silicates coated with amorphous silica.

For the purposes of this invention the substrate particles should havean average diameter greater than about 1 millimicron. Substrateparticles in which the ultimate 2,739,975 Patented Mar. 20, 1956 unitshave diameters of at least 5 millimicrons but less than millimicrons arepreferred. Another preferred type of substrate particles aresupercolloidal aggregates or pulverulent solids.

It is further preferred that the inorganic siliceous solids be porous,that is, they should have exposed surfaces in the interior of theparticle which are available to the exterior so that liquids and gasescan penetrate the pores and reach the exposed surfaces of the porewalls. In other words, the solid forms a three-dimensional network orwebwork through which the pores or voids or interstices extend as alabyrinth of passages or'open spaces.

Especially preferred are porous inorganic siliceous solids havingaverage pore diameter of at least four millimicrons. The large poresafford easy access for alcohol molecules in the subsequentesterification to give the products of the invention.

The substrate particles have large surface areas in relation to theirmass. The term used herein and the one normally so used in the art toexpress the relationship of surface area to mass is specific surfacearea. Numerically, specific surface area will be expressed in squaremeters per gram (m. /g.).

According to the present invention, the substrate parti cles have anaverage specific surface area of at least 1 square meter per gram andpreferably the average specific surface area is at least 25 m. g. In thecase of precipitated amorphous silica, a preferred material, there is anoptimum range of about 200 to 400 m. /g., based on the fact that in thisrange the supercolloidal particles or aggregates can be obtained in adry state without bringing about a considerable collapse of the porousstructure. by replacing the Water with a water-miscible organic solventsuch as acetone and then drying. This powder is especially suitable forsubsequent esterification. It is, of course, possible to produce veryvoluminous aerogels by processes of the prior art, having surface areasof from 200 to 900 m. g. Such highly porous forms of silica can besurface-esterified by the process of this invention.

Specific surface area, as referred to herein, is deter mined by theaccepted nitrogen adsorption method described in an article Anew methodfor measuring the surface areas of finely divided materials and fordeter" mining the size of particles by P. H. Emmett in Symposium on NewMethods for Particle Size Determine tion in Sub-Sieve Range published bythe American Society For Testing Materials, March, 1951, page 95. Thevalue of 0.162 square millimicron for the area covered by one surfaceadsorbed nitrogen molecule is used in calculating the specific surfaceareas.

Pore diameter values are obtained by first determining pore volume fromnitrogen adsorption isotherms as described by Holmes and Emmett inJournal of Physical and Colloid Chemistry 51, 1262 (1947). From thevolume figure, the diameters are obtained by simple geometry assumingcylindrical pore structure.

Determination of gross particle size and shape of substrate material aresuitably made by a number of standard methods whose choice for use in aparticular case depends upon the approximate size and shape of theparticles and the degree of accuracy desired. Thus, for coarsematerials, the dimensions of individual particles or coherent aggregatescan be determined with. the unaided eye and ruler or calipers. For morefinely powdered material, the light microscope is used with a calibratedscale. For materials having a particle size in the range of from 2 or 3microns down to 5 millimicrons, the electron microscope is used.Particle size determination using an electron microscope is described indetail by .T. H. L. Watson in Analytical Chemistry 20, 576 1948).

While various inorganic siliceous solids having the aforementionedproperties can be used as substrate materials in preparation of theproducts of my invention, precipitated amorphous silica is particularlypreferred. Such silica is characterized by Y-rays as lacking crystallinestructure.

' The preparation of several suitable amorphous silicas is illustratedin the examples. For a detailed discussion of sources of amorphoussilica for use in preparing ester; sils of primary and secondaryalcohols, reference should be had to my copending U. S. application,Serial No. 171,759, filed July 1, 1950, now abandoned.

Instead of silica, water-insoluble metal silicates can be used as thesubstrate. Such metal silicates can be prepared, as is well known in theprior art, by treatment of silicas with metal salts or hydrous metaloxides, excluding those containing only alkali metal ions. Such metalsilicates can be prepared so as to have a large number of silanol(-SiOH) groups on the surface of the particle. Thus metal silicateshaving a large proportion of metal ions on the surface may be activatedfor esterification by washing with acids to remove at least a portion ofthe metal ion and leave surface silanol groups.

Crystalline metal silicates occurring in nature can also be used.However, the proportion of silanol groups on most minerals is very smallsince the surfaces also contain metal hydroxy groups, silicon oxygengroups and adsorbed metal ions. Therefore, before esterification it isnecessary to introduce silanol groups on the surface. Loosely adsorbedmetal ions may be exchanged for hydrogen ions by washing the diluteacids or by treatment With ion exchange resins. In some cases, morevigorous treatment, such as reaction with acids at low pH and often atelevated temperatures are required to give a material which will containa suficient number of silanol groups in the surface to yield anorgano-philic product on esterification.

Alternatively or additionally, silanol groups can be introduced on thesurface of metal silicates by coating them with a layer of amorphoussilica. This is accomplished by treating, ay, sodium silicate with anacid in the presence of the mineral silicate particles under suchconditions that the silica formed will deposit as a coating on themineral particle.

Mineral crystalline silicates which can be used in preparing thesubstrate particles are as follows: the asbestos minerals, such aschrysotile asbestos and serpentine (hydrous magnesium silicate)and'amphiboles such as crocidolite asbestos (a sodium magnesium ironsilicate), amosite (an iron silicate), tremolite (a calcium magnesiumsilicate), and anthothyllite (a magnesium iron silicate); claymaterials, such as halloysite (an aluminum silicate), attapulgite (amagnesium aluminum silicate), hectorite (a magnesium lithium silicate),nontronite (magnesium aluminum iron silicates); the kaolins, such askaolinite, nacrite and dickite (aluminum silicate); and bentonites, suchas beidillite, saponite and montmorillonite (magnesi um aluminum ironsilicates); and micaceous minerals, such as phlogopite (a potassiummagnesium aluminum silicate), muscovite (a potassium aluminum silicate,biotite (a potassium iron aluminum silicate) and vermiculite (a hydrousmagnesium iron aluminum silicate).

THE ESTERIFYING AGENT The inorganic siliceous solids described above arereacted with substituted primary and secondary alcohols to give theproducts of the invention. The alcohols herein called esterifying agentsare represented by the formula ROI-I Where R is a substitutedhydrocarbon radical in which the carbon atom attached to the oxygen ofthe hydroxyl group is also attached to at least one hydrogen, thehydrocarbon radical having from 2 to 18 carbon atoms and containing abasic substituent which is attached to a carbon atom at least 1 carbonatom removed from the hydroxyl group and which is capable of formingonium ions. The basic substituent is a member of the class consisting ofamino nitrogen and sulfonium sulfur.

When it is said that the substituent is basic reacting, it is meant thatthe substituent is substantially basic in its chemical reactivity. Whenan alcohol containing a basic substituent is placed in water, its pH'asmeasured by immersing a glass electrode in a'1% solution of the alcoholin water gives an apparent pH reading of at least 9 or higher. If thesubstituted alcohol is not readily soluble in wa.er it may be necessaryto carry out the pH determination in the presence of a 5050 mixture ofwater and methanol.

it will be understood that the basicity of the alcohol is due to thenitrogen and sulfur atoms which are capable of forming onium ions.

As examples of suitable onium forming, nitrogencontaining esterifyingagents there may be named ethanolamine, diethanolamine,beta-diethylaminoethanol, 3- aminopropanol, para-aminobenzyl alcohol,IZ-aminocctadecyl alcohol and alpha-methylbenzyldiethanolarnines.

Suitable esterifying compounds containing a sulfur atom capable offorming sulfoniurn ions include gammahydroxypropyl methyl sulfide,bis-beta-hydroxyethyl sulfide, beta-hydroxyethyl methyl sulfide,beta-hydroxyethyl ethyl sulfide and beta-hydroxyethyl propyl sulfide.These sulfur-containing alcoholsjcau be esteritied With the silicasurface and subsequently reacted with a compound such as, for example,methyl bromide to convert the sulfur atom to sulfonium ions.

Technically, there is no upper limit to the number of carbon atoms whichmay be present in the esterifying agent. As a practical matter, however,the group of al cohols having from 2 to 18 carbon atoms include the.

majority of the common alcohols and offer a selection of molecule sizeswhich should be adequate for any purpose.

Substituted alcohols containing from 3 to 8 carbon atoms are especiallypreferred because they are the most economical to use and yield aproduct having a low ratio of organic matter through silica.

Still more preferred are the amino alcohols. The amino alcohols maycontain a primary, secondary or tertiary amino group.

The esterifying agent will ordinarily contain only one basicsubstituent, but the agent can contain more than one group. The groupsdo not necessarily need to be the same.

The esterifying agent need not be a single alcohol. Mixtures ofsubstituted alcohols can be used. Thus, when a variety of surfaceproperties is desired, a mixture of alcohols may be used. Also, therecan be a mixture of different chain lengths found in the technical gradeof some alcohols. And, if desired, a mixture consisting of anunsubstituted primary or-secondary alcohol and an alcohol containing abasic substituent group can be used.

ESTERIFICATI ON silica. The external surface can then be reacted withalcohol.

The inorganic siliceous solid is preferably freed of extraneous materialbefore esterification, and the pH is adjusted to avoid strong acids oralkalis in the reaction. The pH is preferably 5 to 8.

The amount of water present in the reacting mass during theesterification step has an important bearing on This can be done bytreatment with' since the esterific'ationprocess is an equilibriumreaction, it is ordinarily desirable to keep the Water content as'low aspossible during the course of..the reaction.

In order to esterify sufiiciently to obtain a high proportion ofsubstituted ester groups on thesurface ofuthe siliceousparticles, theWater in the liquid phase of the.

system should not exceed about 5% by weight of that phase. For maximumesterification, the water content must be kept below about 1.5%. Asalready mentioned, it is desirable to keep the water content tas low aspossible.

Because of the hindering effect of watenon the esterification, if thesiliceous solid to be esterified iswet, the free water must be removedeither before the solid is put into the alcohol or alternatively it maybe removed 1 by distillation after mixing with the alcohol.

Simple air drying at temperatures of from 100 to 150 C. will remove mostof the free water. Drying may be hastened by the application of vacuum.For many types of siliceous solids, however, air drying is ,notsatisfactory because they tend to shrink to hard, compact masses upondrying from water.

Water can suitably be removed from a wet siliceous solid beforeesterification by displacing the water in the wet mass with a polarorganic solvent such as acetone. The solvent can later be recovered.

Preferably, water is removed from wet siliceous solids prior toesterification by azeotropic distillation. Thus, Water-wet cake can bemixed with a polar organic solvent such as methyl ethyl ketone and themixture distilled until the system is freed from water. The organicsolvent can then be evaporated to give a dry product for reaction withalcohol.

Alternatively, the alcohol which is to be used as the esterifying agentcan also be used in some instance s as the azeotropic dehydrating agent.

The ratio of alcohol and siliceous material to be used in theesterification is limited only by the fact that the alcohol should bepresent in sufiicient excess to facil itate a practical rate ofreaction. i referably, 'sutficient alcohol is used to provide a slurryof the siliceous material in alcohol which can be readily stirred. Ofcourse, larger portions of alcohol must be used when no water is removedfrom the system during the reaction. The

reason for this being that the reactionliberateswater. and may exceedthe maximum permissible value unless alcohol is added either before or.during the'reaction step.

In general, it is sufficient to carry out the esterification by simplyrefluxing the mixture of the silica and the al cohol together for asuitable length of time, for example, upwards of 2 hours. in cases Wherethe alcohol is somewhat unstable, it may be desirable to carry out the,esterification at somewhat lower temperatures than the boiling point ofthe arcohol in order to preventthe excessive decomposition in the liquidphase. A preferred method of using unstable alcohols as esterifyingagents comprises heat-activating the, silica and chemically reacting thealcohol with the resulting surface-activated silica in accordance withthe invention described and claimed in the copending application of MaxT. Goebel, Serial No. 261,140, filed December ll, 1951. I

alcohol, onecskilled in the art may learn from. the 'data the generalprinciples involved and conclude what conditions shouldbe used for.another alcohol.

The temperatures,substantiallybelow about 100 C. are not suitable inmostinstances. h scrbed on. the siliceous surface at such. temperatures buttrue esterification is not obtained.

The esterified temperature should not exceed thethermal decompositionpoint of the alcohol while in the presence of siliceous solids. Norshould it exceed the point of thermal stability of the esterifiedsiliceous materials. Preferably, the heating is not prolonged any morethan is required to achieve esterification equilibrium. As alreadyindicated, the reaction between amorphous silica and liquid alcohols canbe carried out by autoclaving a slurry of the silica in an excess of theorganic reagent. However, when the alcohol is high melting, or unstableabove its melting point, it is preferred to carry out the reaction in adilute solution, say, 10% of the organic reagent in an inert solvent,such as, for instance, benzene, toluene, xylene, trichloroethylene,dioxane and dibutyl ether of ethylene glycol.

Whether the reaction is effected at atmospheric pressure, at the refluxtemperature of the solution or under autoclave conditions will largelydepend on the boiling point of the solvent used; that is, whether theboiling point is high enough to effect substantial reaction beween thesilica and the esterifying agent. Occasionally, it is desirable todeposit a mono layer of the alcohol uniformly over the silica surface bystirring the latter with a solution of the alcohol in alow boiling,inert solvent suchas ether or acetone, and then evaporating the solventwhile maintaining constant agitation. Complete reaction is'then eifectedby heating the dry, coated product to a temperature sufficiently high tocause removal of water.

After completion of the esterification, the product estersils canbe'removed from the unreacted alcohol by conventional methods. Thus, theseparation can be made by filtration in those instances wherein theestersils consist of particles of-supercolloidal size. These estersilsare retained on ordinary filter media.

Alternatively, the alcohol can be vaporized by applying vacuum to thereaction vessel. Or where the alcoholis one' which will distill atatmospheric pressure without decomposition, simple distillation can beused; In 'the case of higher alcohols which are not readily distilled,except under very high vacuum, the alcohol can In adddtion, when thealcohol to. be used israther. low a boiling, that is, less than 100 (1.,in order to promote more complete reaction than could be realized. atthe boiling point, it may be desired to carry out the esterification inthe autoclave at temperatures from ZOO-300 C.

The extent of the reaction is fixed more by the temperature than by thetime, that is, at a suitabletemperature the esterification reactionproceeds quite. rapidly up to a certain point which is characteristic ofthe temperature and of the alcohol and thereafter proceedsslowly.

The minimum reaction time and temperaturein order to obtain any givenextent of. reaction varies with'the be extracted from the product with alow boiling solvent such as,'for instance, methyl ethyl ketone,chloroform or ether.

PROPERTIES AND USES OF THE PRODUCTS The products of the invention are inthe form of powders or sometimes lumps or cakes which are pulverableunder the pressure of the fingeror by a light rubbing action. Theesterifield inorganic siliceous solids are exceedingly 'fine, light,fluffy, voluminous powders The esterification reaction does notsubstantially change the structure of the inorganic siliceous solid orsubstrate which was esterified. In other words, the internal structureof the estersil, the structure to which the 'OR groups are chemicallybound, has substantially the same particle size, surface area and othercharacteristics described previously in the discussion of thesubstratematerial. The estersils of the invention are in a colloidal orsupercolloidal state of subdivision.

The products of the invention can be hydrophilic or orgahophilicdepending on the particular alcohol employed as the esterifying agentand also on the type and number of basic substituents per R gIQUP- Ingen eral, the products will behydrophilic due to the presence Alcoholmay be ad 7 an their surfaces of the polar basic substituent group. if along chain alcohol is employed, the resulting product nay also beorganophilic.

By the term organophilic I mean that when a pinch of estersil is shakenin a two-phase liquid system of water and n-butanol in a test tube theproduct will Wet" into the n-butanol phase in preference to the waterphase.

The number of ester groups for 100 square millimicrons of siliceoussubstrate surface is calculated from the expression Surface area w w 12nS X 1015 n X Sn where C is the weight of the carbon in grams attached to100 grams of substrate; n is the number of carbon atoms in the ORgroups; Sn is the specific surface area in m. g. of the substrate asdetermined by nitrogen adsorption.

Where the sample to be analyzed is one in which the type of alcohol isunknown, the sample can be decomposed with an acid and the alcohol canbe recovered and identified. The specific surface area of the substratecan be determined by first burning off the ester groups, as for example,by slowly heating the estersil in a stream of oxygen up to 500 C.and'holding it at that temperature for a period of about three hours andthen rehydrat ing the surface of the particles by exposure to 100%relative humidity at room temperature for several hours and finallydetermining the surface area of the remaining solid by nitrogenadsorption method.

In the products of the invention the OR groups are chemically bound tothe substrate. The products should not be confused with compositions inwhich an alcohol is merely physically adsorbed on the surface of thesiliceous solid. Adsorbed alcohols can be removed by. heating thematerial at relatively low temperature, for example, 150 C. under highvacuum, say, 10 millimeters of mercury for a period of one hour. Incontrast, the products of my invention are stable under such treatment.Neither can the ester groups be removed by washing with hot methyl ethylketone or similar solvents or by prolonged extraction in a Soxhletextractor. In case of ordinary physical adsorption thealcohol isdisplaced by such treatment.

When esterification is effected with an amino alcohol, the presence ofthe basic amino group in the product can be shown by the high pH of aslurry of the product in water. Thus, for instance; the pH of a slurryis within the range of 910. Additionally or alternatively, the basicamine groups on the surface of the estersil may be titrated withstandard acid.

It has already been observed that the products of the invention areabsorbents for acidic materials. Using an acidic substance such as anacid dye, it can be further demonstrated that amine groups are presenton the surface of esterified silica. By slurrying a product of thepresent invention for a brief period, say, five minutes, with a solutionof an acid dye, collecting the product, washing it with water and etherand finally drying, a dyed product is obtained. Control samples ofunesterified silicas and siliceous powders esterified with unsubstitutedaliphatic alcohols are not dyed under identical conditions.

The products of the invention are useful as adsorbents for acidicsubstances, especially acid dyes, and as fillers for polymericmaterials. The products find particular utility as fillers for polymericsubstances where the polymer contains an acidic substituent. The lattermay react with the basic substituent from the estersil surface to yielda chemically integrated structure. The products are also useful asfillers for elastomers such as, for instance, silicone rubber.

In order that the invention may be better understood a a referenceshould be had to the following illustrative examples: a

' Example 1 This is an example of a process of this invention wherein asiliceous powder consisting'of coherent aggregates of coalesced, dense,ultimate units is esterfied with beta-diethylaminoethanol.

A silica sol was prepared in the following manner: A solution of sodiumsilicate, having an SiO2:Na2O mole ratio of 3.36, and containing 3.64grams of SiOz per 100 milliliters, was heated to 95 C. To ten volumes ofthis hot silicate solution 1 volume of a 2.9 N sulfuric acid solutionwas added over a period of one-half hour, at a uniform rate, and withvigorous agitation. The final SiOz concentration was 3.3% and ofthe NazOoriginally present in the sodium silicate solution was neutralized, is,the final SO3:Na2O mole ratio was equal to 0.8.

The Na+ ion concentration was maintained at less than 0.4 N throughoutthe process and the final pH of the sol was about 10. In this manner anopalescent silica $01 was prepared, the particles of which were about 15millimicrons in diameter as determined from electron micrographs..Hereafter, a silica sol prepared in the above manner will be referred.to as the heel.

To a heel prepared in'this' manner equal volumes of sodium silicatesolution (SiOzzNazO mole ratio=3.36) and a sulfuric acid solution wereadded simultaneously but separately with'vigorous agitation over .a twohour period, whilethe temperature was maintained at C.

The concentration of the sodium silicate solution was about 6.6 grams ofSiOs'per milliliters and a sufficient volume was added over the two hourperiod so that two parts of SiOz were added for each part of SiOzoriginally present in the heel. The concentration of SiOz in the silicasol or slurry was maintained at 3.3 grams of SiOz per 100 millilitersthroughout the preparation. The con centration of the sulfuric acid(0.52 N) was adjusted so that at all times the ratio of S03 to NazO inthe solution was 0.8, i. e., a pH of about 10 was maintained. The Na+ion concentration was maintained at less than 0.4 N throughout theprocess.

Early in the build-up process the particles of silica present in theheel started to coalesce and precipitate. The final slurry was filtered,the wet filter cake was reslurried in water, and coagulated with 0.2% byweight (based on SiOs) of a mixture of equi-molar portions of cetyl andlauryl trimethylammoniurn bromide. The pH was adjusted to about 8 with 4molar sulfuric acid, the reslurry was filtered, washed, and the cake wasdried and the soft, pulverable product was powdered in the Raymond mill.

The dried powder consists of coherent aggregates of coalesced, denseultimate units having an average unit diameter of about 25 millimicrons.The specific surface as measured by nitrogen adsorption was 97 squaremeters per gram, and the specific hydroxylated surface area was 97square meters per gram as measured by methyl red adsorption. A slurry of4 grams of the silica in 40 cc. of distilled water had a pH of 8.2.

The dry silica powder prepared according to the above method was furtherdried in vacuum at a temperature of 70 C. Ninety-three parts by weightwere then added.

to 500 partsby volume of beta-diethylaminoethanol. The resulting slurrywas charged to a pot fitted'for reflux, and the temperature of theslurry was slowly raised. The slurry formed a thick mixture,particularly around 60-70 C., which thinned out as the temperatureincreased to 100 C. and above. A little water was distilled ofi at 100C., and the mixture started to boil at 154 C. The mixture was.maintained at boiling point for a period of 1% hours. The temperature ofthe mixture gradually rose to C.

The slurry was allowed to cool. It was then filtered.

armors 9 The filter-cake was collected, slurried with ethanol threetimes, collected and finally dried from a steam bath.

The resulting material was a white free-flowing powder, which was foundto contain 1.51% carbon by chemical analysis. Based on the carbonanalysis and the specific surface area, this corresponds to 130substituted ester groups per 100 square millimicrons of silica surface.

When 4 grams of the final product were slurried in 40 milliliters ofdistilled water, the pH was found to be 9.6. This demonstrated thepresence of the amine groups on the esterified surface.

Two-tenths parts by Weight of the esterified silica was agitated for aperiod of 7 minutes at room temperature with an excess of a 0.1% aqueoussolution of an acid dyestufi having Colour Index Number 278 (U. S.Patent 931,423) containing 0.1% H2804. At the end of the treatment time,the dye solution was removed by filtration, and the solid was washed onthe filter paper with 50 parts by volume of ethyl ether, each in smallportions. The resulting powder was dried and was found to be dyed a deepred color. In contrast, an unesterified control sample was treated inexactly the same manner, and was found to remain colorless.

Example 2 Twenty-five parts by weight of the dry silica powder,consisting of coherent aggregates of coalesced, dense, ultimate units,prepared as in Example 1, was heated in an excess ofalpha-methylbenzyldiethanolamine to a temperature of 225 C., and finallyallowed to cool. The silica was removed from the slurry by filtrationand the resulting wet-cake was washed with ethanol by filtering threetimes. The filter cake was finally dried on a steam bath and then in anoven.

Two-tenths part by weight of the resulting dry estersil was treated atroom temperature with 0.1% aqueous solution of a dyestutf having ColourIndex No. 1078 (U. S. Patent 599,426), containing 0.1% sulfuric acid, byagitating the slurry for a period of seven minutes. The dye solution wasremoved by filtration and the solid material washed on the filter paperwith 50 parts by volume of water, 25 parts by volume of ethanol andparts by volume of ethyl ether, each in small portions. The resultingmaterial was dried and was found to be dyed a bluish green. In contrast,an unesterified control was not dyed by a similar treatment.

Example 3 This is an example of the esterification of 17 millimicron,dense silica particles with ethanolamine.

Two hundred parts by volume of a commercially available 30% silica solconsisting of 17 millimicron colloidal particles and known as Ludoxcolloidal silica was deionized by successive passes through a bed of acation and then an anion exchanger. The resulting sol was charged to adistilling vessel, fitted with a packed column, a stirrer, and athermometer, 450 parts by volume of ethanolamine was added to thevessel.

The temperature of the mixture of sol and ethanolarnine was graduallyincreased. Water was distilled from the mixture. At a temperature of 137C. the material gelled quite suddenly, and distillation was stopped. Theexcess ethanolamine was removed under vacuum while the mixture washeated on a steam bath. The resulting solid was washed with ethanol byslurrying and filtering three times. The resulting material was dried ona steam bath.

The resulting dry powder was found to contain 1.99% carbon by chemicalanalysis. Based on the carbon analysis and a specific surface area of175 m. /g., this corresponds to a degree of esterification of about 285substituted ester groups per 100 square millimicrons of silica surface.

Four grams of the dried sample was slurried in 40 ml. of distilled waterto demonstrate the basic nature of the it) esterified surface. Theresulting pH was found to be 9.0.

I claim:

1. A solid consisting essentially of substrate particles or" inorganicsiliceous material having an average specific surface area of from 1 to900 square meters per gram, and an average particle diameter greaterthan about 1 millimicron, having chemically bound to the silicon atomson the surface of said particles at least 100 -OR groups per 100 squaremillimicrons of surface area of the siliceous material, where R is asubstituted hydrocarbon radical having from 2 to 18 carbon atoms and inwhich the carbon attached to oxygen is also attached to at least onehydrogen atom, said substituted hydrocarbon radical containing a basicsubstituent attached to a carbon atom at least 1 carbon atom removedfrom the oxygen atom of the OR group, the substituent being selectedfrom the class consisting of nitrogen and sulfur atoms capable offorming onium ions.

2. A solid consisting essentially of substrate particles of inorganicsiliceous material having an average specific surface area of from 1 to900 square meters per gram, and an average particle diameter greaterthan about 1 millimicron, having chemically bound to the silicon atomson the surface of said particles at least 100 OR groups per 100 squaremillimicrons of surface area of the siliceous material, Where R is asubstituted hydrocarbon radical having from 2 to 18 carbon atoms and inwhich the carbon attached to oxygen is also attached to at least onehydrogen atom, said substituted hydrocarbon radical containing a basicsubstituent attached to a carbon atom at least 1 carbon atom removedfrom the oxygen atom of the OR group the basic substituent beingselected from the class consisting of amino nitrogen and sulfoniumsulfur.

3. A powder consisting essentially of substrate particles of amorphoussilica in a supercolloidal state of subdivision having an averagespecific surface area of from 1 to 900 square meters per gram, and anaverage particle diameter greater than about 1 millimicron, havingchemically bound to the silicon atoms on the surface of said particlesat least OR groups per 100 square millimicrons of surface area ofsubstrate surface, where R is a substituted hydrocarbon radical havingfrom 2 to 18 carbon atoms and in which the carbon attached to oxygen isalso attached to at least one hydrogen atom, said substitutedhydrocarbon radical having a basic substituent attached to a carbon atomat least 1 carbon atom removed from the oxygen atom of the -OR group,the basic substituent being selected from the class consisting of aminonitrogen and sulfonium sulfur.

4. A powder consisting essentially of substrate particles of amorphoussilica in a supercolloidal state of subdivision having an averagespecific surface area of from 1 to 900 square meters per gram, and anaverage particle diameter greater than about 1 millimicron, and havingchemically bound to the silicon atoms on the surface of said particlesat least 100 -OR groups per 100 square millimicrons of surface area ofthe siliceous material, where R is a substituted hydrocarbon radicalhaving from 2 to 18 carbon atoms and in which the carbon attached tooxygen is also attached to at least one hydrogen atom, said substitutedhydrocarbon radical containing a basic nitrogen substituent capable offorming onium ions attached to a carbon atom at least 1 carbon atomremoved from the oxygen atom of the OR group.

5. A powder consisting essentially of substrate particles of amorphoussilica in a supercolloidal state of subdivision having an averagespecific surface area of from 200 to 900 square meters per gram, and anaverage particle diameter greater than about 1 millimicron, having anaverage pore diameter of at least 4 millimicrons, and having chemicallybound to the silicon atoms on the surface of said particles at least 100-OR groups per 1430 square millimicrons of surface area of the siliceousmaterial, where R is a substituted hydrocarbon radical hav- '11 ing from2 to 18 carbon atoms and in which the carbon attached to oxygen is alsoattached to at least one hydrogen atom, said substituted hydrocarbonradical containing a basic nitrogen substituent attached to a carbonatom at least 1 carbon atom removed from the oxygen atom of the --ORgroup.

6. A process which comprises the step of chemically reacting an alcoholof the formula ROH in which R is a substituted hydrocarbon radicalhaving from 2 to 18 carbon atoms, wherein the carbon atom attached tooxygen is also atatched to at least one hydrogen, said radicalcontaining a basic substituent attached to a carbon atom at least 1carbon atom removed from the hydroxyl group, the substituent beingselected from the class consisting of nitrogen and sulfur atoms capableof forming onium ions, with an inorganic siliceous material which issubstantially free of strong acids and alkalis and has an averagespecific surface area of from 1 to 900 square meters per gram and anaverage particle diameter greater than about 1 millimicron, and areactive surface containing groups selected from the class consisting ofsilanol and heat-activated silicon-oxygen groups, while maintaining thewater content of the system below about 5 per cent by weight of thealcohol in the system and the temperature in the range from 100 C. tothe thermal decomposition temperature of the alcohol.-

7. A process which comprises the step of chemically reacting at a pH of5 to 8, an alcohol of the formula ROH in which R is a substitutedhydrocarbon radical having from 2 to 18 carbon atoms, wherein the carbonatom attached to oxygen is also attached to at least one hydrogen, saidradical containing a basic substituent attached to a carbon atom atleast 1 carbon atom removed from the hydroxyl group, the substituentbeing selected from the class consisting of amino nitrogen and sulfoniumsulfur with an inorganic siliceous material having an average specificsurface area of from 1 to 900 square meters per gram and an averageparticle diameter greater than about 1 millimicron, and having areactive surface con taining groups selected from the class consistingof silanol and heat-activated silicon-oxygen groups, While maintainingthe water content of the system below about 5 per cent by weight of thealcohol in the system and the temperature in the range from 100 C. tothe thermal decomposition temperature of the alcohol.

8. A process which comprises the step of chemically reacting at a pH of5 to 8, an alcohol of the formula .ROH in which R is a substitutedhydrocarbon radical surface containing groups selected from the classconsisting of silanol and heat-activated silicon-oxygen groups, whilemaintaining the water content of the system below about 5 per cent byweight of the alcohol in the system and the temperature in the rangefrom C. to the thermal decomposition temperature of the alcohol.

9. A process which comprises the step of chemically reacting at a pH of5 to 8, an alcohol of the formula ROH in which R is a substitutedhydrocarbon radical having from 2 to 18 carbon atoms, wherein the carbonatom attached to oxygen is also attached to' at least one hydrogen, saidradical containing a basic substituent attached to a carbon atom atleast 1 carbon atom removed from the hydroxyl group, the substituentcontaining amino nitrogen, with an inorganic siliceous material in asupercolloidal state of subdivision, having an average specific surfacearea of from 1 to 900 square meters per gram, and an average particlediameter greater than about 1 millimicron, and having a reactive surfacecontaining groups selected from the class consisting of silanol andheat-activated silicon-oxygen groups, 'while maintaining the watercontent of the system under about 5% by weight of alcohol in the systemand the temperature in the range from 100 C. to the thermaldecomposition temperature of the alcohol until at least 100 OR groupsper100 square millimicrons 'of surface area of said inorganic siliceoussolids are chemically bound thereto.

References Cited inthe file of this patent UNITED STATES PATENTS1,594,627 Meyers Aug. 3, 1926 1,868,422 Luecke July 19, 1932 2,251,496Parsons Aug. 5, 1941 2,325,217 Beers July 27, 1943

1. A SOLID CONSISTING ESSENTIALLY OF SUBSTRATE PARTICLES OF INORGANICSILICEOUS MATERIAL HAVING AN AVERAGE SPECIFIC SURFACE AREA OF FROM 1 TO900 SQUARE METERS PER GRAM, AND AN AVERAGE PARTICLE DIAMETER GREATERTHAN ABOUT 1 MILLIMICRON, HAVING CHEMICALLY BOUND TO THE SILICON ATOMSON THE SURFACE OF SAID PARTICLES AT LEAST 100 -OR GROUPS PER 100 SQUAREMILLIMICRONS OF SURFACE AREA OF THE SILICEOUS MATERIAL, WHERE R IS ASUBSTITUTED HYDROCARBON RADICAL HAVING FROM 2 TO 18 CARBON ATOMS AND INWHICH THE CARBON ATTACHED TO OXYGEN IS ALSO ATTACHED TO AT LEAST ONEHYDROGEN ATOM, SAID SUBSTITUTED HYDROCARBON RADICAL CONTAINING A BASICSUBSTITUTENT ATTACHED TO A CARBON ATOM AT LEAST 1 CARBON ATOM REMOVEDFROM THE OXYGEN ATOM OF THE -OR GROUP, THE SUBSTITUENT BEING SELECTEDFROM THE CLASS CONSISTING OF NITROGEN AND SULFUR ATOMS CAPABLE OFFORMING ONIUM IONS.
 7. A PROCESS WHICH COMPRISES THE STEP OF CHEMICALLYREACTING AT A PH OF 5 TO 8, AN ALCOHOL OF THE FORMULA ROH IN WHICH R ISA SUBSTITUTED HYDROCARBON RADICAL HAVING FROM 2 TO 18 CARBON ATOMS,WHEREIN THE CARBON ATOM ATTACHED TO OXYGEN IS ALSO ATTACHED TO AT LEASTONE HYDROGEN, SAID RADICAL CONTAINING A BASIC SUBSTITUENT ATTACHED TO ACARBON ATOM AT LEAST 1 CARBON ATOM REMOVED FROM THE HYDROXYL GROUP, THESUBSTITUENT BEING SELECTED FROM THE CLASS CONSISTING OF AMINO NITROGENAND SULFONIUM SULFUR WITH AN INORGANIC SILICEOUS MATERIAL HAVING ANAVERAGE SPECIFIC SURFACE AREA OF FROM 1 TO 900 SQUARE METERS PER GRAMAND AN AVERAGE PARTICLE DIAMETER GREATER THAN ABOUT 1 MILLIMICRON, ANDHAVING A REACTIVE SURFACE CONTAINING GROUPS SELECTED FROM THE CLASSCONSISTING OF SILANOL AND HEAT-ACTIVATED SILICON-OXYGEN GROUPS, WHILEMAINTAINING THE WATER CONTENT OF THE SYSTEM BELOW ABOUT 5 PER CENT BYWEIGHT OF THE ALCOHOL IN THE SYSTEM AND THE TEMPERATURE IN THE RANGEFROM 100*C. TO THE THERMAL DECOMPOSITION TEMPERATURE OF THE ALCOHOL.